Is the Sony FE 70-200mm F4 G OSS Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 100mm f/11.0 test image. Observe the contrast and resolution of these results.
Is the Sony FE 70-200mm F4 G OSS Lens set to 100mm f/11.0 sharper than the Sigma 100-400mm f/5-6.3 DG DN OS C Lens set to 135mm f/6.3? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.